The present invention relates to a chuck for a machine tool or shop machine and includes a chuck body that is provided with a frusto-conical opening that has guide surfaces, whereby a clamping or chuck head or member is adapted to be received in the opening of the chuck body, with the clamping head having an axially extending receiving opening for workpieces, cooperating with a drawing mechanism, and being provided with gripping jaws that have cooperating or mating guide surfaces, whereby the guide surfaces of the frusto-conical opening of the chuck body have a pressure connection with the mating guide surfaces of the gripping jaws.
A chuck of the aforementioned general type is disclosed, for example, in EP 0 258 771. In heretofore known chucks, the gripping jaws have the shape of a portion of a truncated cone surface and are interconnected by elastomeric spring elements. A complete pressure connection between the gripping jaws and the guide surface is possible in only a single position of the gripping jaws relative to the chuck body, since when the gripping jaws are axially displaced, those portions of the gripping jaws and guide surfaces that correspond with one another have different guide radii. In addition, when the clamping head is introduced into the chuck body, the spacing between the gripping jaws is also reduced, which can lead to a further imprecision of the concentricity o ability of the workpiece to run true.
Proceeding from the aforementioned state of the art, it is an object of the present invention to improve a chuck of the aforementioned general type in such a way that a trueness can be maintained with a precision of less than 10.sup.-2 mm.